Intrauterine growth retardation and diabetic pregnancy: two types of fetal malnutrition.

Placental transfer of alpha-aminoisobutyric acid and methylglucose was studied near term in normal guinea pigs carrying growth-retarded fetuses and in streptozotocin-treated diabetic guinea pigs. Compared with their normal littermates, growth-retarded fetuses had lower placental weights and a diminished transfer of both nutrient analogues in proportion to the reduction in fetal weight. Fetuses from diabetic animals had normal fetal weight and placental methylglucose transfer but reduced litter size and a 40% reduction in placental alpha-aminoisobutyric acid transfer. These data suggest that intrauterine growth retardation in an otherwise normal pregnancy is associated with a small placenta and a reduced transfer of nutrients. Diabetic pregnancy may represent a different type of fetal malnutrition due to amino acid deprivation. It is speculated that birth weight does not necessarily reflect the degree of fetal malnutrition in diabetic pregnancy since fetal growth may be maintained by glucose and fat deposition.